Whenever I talk to grandparents they think it's not them but the ­parents who are ­overindulgent about food. When we were ­children we ate what we were given and left a clean plate. Now, some parents offer choices at every meal or allow their children to blackmail them to give them what they want.

I have six grandchildren and when I have them with me I do love giving them treats – ice-cream or a bar of chocolate. But they are given as a surprise reward for behaving well, not in response to whingeing.

One reason so many ­children are more overweight today could be that they lead less active lives than we did. We walked to school and spent more time playing in the fresh air. Houses were not as warm, so we used up more calories: food was fuel to keep us going. If grandparents are feeding grandchildren the same portions they ate as children, it's probably too much.

I don't think many grand­parents just plonk children in front of the television. Most like to have a kick about in the park. This winter I went tobogganning on a teatray with mine – I thought it might be the last time I had the chance! We do lots of outdoors things, such as going for walks in the woods. But rather than calling it "going for a walk", I say, "Let's go to the wild woods."

I would suggest involving children in cooking. I have ­discovered, from Hugh, that if you want children to eat their greens you need to chop up some garlic – very finely – cook it in a little butter, and toss the greens in that. They think it's really tasty. I must admit, we also give our grandchildren ice-cream – but we make it at home with lots of fresh fruit and whizz it up with some cream and sugar. Or we give them fruit jelly – made with pureed fruit and gelatine – children ­always think that's a real treat. And it helps towards their five a day.

It's a wonderful relationship between children and grandparents, and grandparents really want their grandchildren to be healthy. We will readily do all we can to keep them that way.